Abstract: A call button replacement circuit includes a controllable solid state switch that has a control terminal and a two-terminal output circuit, a manually operated switch, an indicator device, and a capacitor. The solid state switch is connected in circuit between a high voltage terminal and a call-acknowledge terminal; the manually operated switch is connected between the high voltage terminal and the control terminal of the solid state switch so that momentary actuation of the manually operated switch places the solid state switch in conducting condition and applies a call signal to the call-acknowledge terminal; the capacitor is connected between the call-acknowledge terminal and the control terminal, and the indicator device is connected in circuit with the solid state switch so that it is energized and produces a light output when the solid state switch is in conducting condition.